Technical Program

Plenary Speakers

Area 1: Jean-François Guillemoles, French National Centre for Scientific Research (CNRS)

Hot Carrier Solar Cells: Myths and Realities

JF Guillemoles is a CNRS Research Director at IRDEP, a joint EDF-CNRS-ENSCP lab and Director of NextPV an international joint lab between CNRS and the RCAST (University of Tokyo), where he is also visiting professor. He is currently active on high efficiency concepts for solar energy conversion (Hot Carriers, Intermediate Band, Multijunctions, Nanophotonics), luminescence-based characterization techniques (esp. Hyperspectral imaging), and modeling of photovoltaic materials and devices. He is author/co-author of more than 300 publications (peer-reviewed papers, book chapters, patents, proceedings, etc.).

Area 2: Markus Gloeckler, First Solar, Inc.

The Adolescence of Cadmium Telluride Photovoltaics

Dr. Markus Gloeckler serves as the Chief Scientist at First Solar. He also oversees all advanced research functions, which over the past five years, have drastically increased the efficiency entitlement of CdTe PV. Dr. Gloeckler received a PhD from Colorado State University and after 15 years in the field, continuous to marvel at the complexity of the device physics of thin-film materials.

Area 3: Stefan Myrskog, Morgan Solar, Inc.

Dr. Stefan Myrskog is Chief Scientist at Morgan Solar. He received his Ph.D. in 2004 from the University of Toronto in the field of ultra-cold atomic physics. He got his start in photovoltaics through his post-doctoral fellowship working with colloidal lead-sulphide quantum dot devices. In 2008 he joined Morgan Solar where he has combined his optics and photovoltaics backgrounds in the development of CPV.

Bifacial silicon solar module has received considerable attention in recent years due to increasing the performance of photovoltaic plants. The passivated emitter and rear cell (PERC) bifacial silicon solar cell reduces contact recombination, and improves open-circuit voltage and cell performance. The recombination parameter J0 is not only an important parameter to characterize device structure and processes for their application, but also a key parameter for simulation in solar cells. In this paper, the recombination behaviour of passivated emitter and rear cell (PERC) bifacial silicon solar module under different illuminations was investigated. It is found that the J01 of bifacial PERC solar module is always lower than that of conventional Al-BSF solar module no matter how irradiance intensity changes. A interesting findings is that the J01 decrease with increasing irradiance intensity. This is because that the SRH recombination may be strongly suppressed in high injection. And the J02 of conventional Al-BSF solar module increase with increasing illumination intensity. The J02 of bifacial PERC solar module is nearly constant from low injection to high injection. The low recombination parameter J0 of PERC solar cells increases their open-circuit voltage, and reduces their temperature sensitivity. So the PERC bifacial silicon solar module has more advantage in the field compared to Al-BSF solar module. The results are beneficial to understanding reduced module operating temperature and good output under low injection of PERC bifacial silicon solar module.

Area 4: Pietro Altermatt, Trina Solar, Limited

Pietro P. Altermatt's main area of research has been the development of physical models for the numerical simulation of crystalline silicon solar cells and testing devices, including ray tracing and numerically solving the Maxwell equations. Of equal interest to him is the application of these models to simulation strategies tailored to research, development and particularly mass production. Such simulations form the quantitative basis for roadmaps, predicting the optimum device design, the necessary production equipment, and the feasible silicon material. He is principal scientist at the State Key Laboratory for PV Science and Technology (SKL) at Trina Solar Ltd. in Changzhou, China. He pursues his non-commercial and academic activities with the Global Photovoltaic Simulation Group, Geneva, Switzerland.

Considering the panel scale in urban environment, standard testing condition is very strong light, does not fully reflect the electricity production capability of solar panels owing to performance degradation under oblique and weak illumination. The simple modification of the module fabrication process including PDMS coatings and 3-dimensional structured module by one directional angled array of each cell have revealed 13.4% more hidden electricity of solar panels. High transmission to short wavelength light and re-capturing the light reflected from Si solar cell surface textures by PDMS coating, enhanced power production under oblique incident light or scattered light through 3-dimensional module.

Area 5: David S. Ginger, University of Washington

Probing Nanoscale Heterogeneity in Thin Film PV: Perovskites to Polymers

David S. Ginger is the Alvin L. and Verla R. Kwiram Professor in Chemistry, a Washington Research Foundation Distinguished Scholar in Clean Energy, an Adjunct Prof. of Physics, and serves as the Chief Scientist of the UW Clean Energy Institute. He is known for his work on the optoelectronic and photonic properties of nanostructured materials, and as a pioneer in the application of new scanning probe microscopy methods. He has been recognized with the Burton Medal of the Microscopy Society of America, fellowship in the AAAS, as a Research Corporation Scialog Fellow and Cottrell Scholar, Alfred P. Sloan Foundation Research Fellow, Camille Dreyfus Teacher-Scholar, and as a Finalist for the Blavatnik Award for Young Scientists. He received the Presidential Early Career Award for Scientists and Engineers, the ACS Unilever Award in Colloid and Surfactant Science, and participated in the 2012-2013 class of the Defense Science Study Group. He is an Associate Editor for ACS Chemical Reviews. Prof. Ginger holds double B.S. degrees in Chemistry and Physics from Indiana University, and a Ph.D. in Physics from the University of Cambridge, U.K, where he studied as a Marshall Scholar and NSF Graduate Fellow. He was an NIH and DuPont Postdoctoral Fellow at Northwestern prior to joining UW in 2003.

Abstract - Single layer Molybdenum disulfide (MoS2), a direct band gap transitional metal dichalcogenide (TMDC) has attracted a lot of research and study due to its excellent electro-optical integrity. Optical absorption within this monolayer MoS2 is extremely influenced by the presence of sulphur vacancies. At reduced dimensions the interaction between these vacancy created trap centres and charge carriers becomes more prominent leading to the formation of bound excitons. Here we demonstrate the absorption spectra of a single layer MoS2 through many body perturbation theory in the presence of sulphur vacancy sites. We use a fully relativistic approach within the GW approximation containing the non collinear core correction with full spinor wave functions. The absorption spectra calculation is achieved through the Bathe-Salpeter equation to include the excitonic excitations at room temperature. Our computations exhibit a Gaussian absorption spectra observed with double excitonic peaks A and B, unlike the step function profile without the incorporation of excited states. This double peak corresponds to valence band splitting at the K point of the brillouin zone which is most prominent at the top of the valence band and is a result of spin orbit coupling of the excitons. The absorption edge demonstrates a red shift when investigated in the presence of sulphur vacancies which can be attributed to inter excitionic interactions and the reduction in bandgap in the presence of sulphur vacancies. A change in the value of absorption coefficient is observed as a result of localization of excitons in the traps. Our outcomes clarify the vacancy and exciton material science of MoS2 offering another course towards fitting its physical properties by defect engineering.

Area 6: Michael McGehee, Stanford University

Making Perovskite Tandem Solar Cells Efficient and Stable Enough to be a Gamechanger

Michael D. McGehee is a Professor in the Materials Science and Engineering Department and a Senior Fellow of the Precourt Institute for Energy. His research interests are developing new materials for smart windows and solar cells. He has taught courses on nanotechnology, nanocharacterization, organic semiconductors, polymer science and solar cells. He received his undergraduate degree in physics from Princeton University and his PhD degree in Materials Science from the University of California at Santa Barbara, where he did research on polymer lasers in the lab of Nobel Laureate Alan Heeger. He won the 2007 Materials Research Society Outstanding Young Investigator Award. He is a cofounder of Iris PV and his former students have started more than ten companies.

Using rigorous coupled wave analysis (RCWA) for simulating absorption in GaAs0.73P0.27 and In0.81Ga0.19As nanowire (NW) arrays grown on 200 μm-thick active silicon substrate, geometrical parameters of the arrays corresponding to maximum broad-band absorption were established. Conditions for current matching between the NW and Si sub-cells were designed by optimizing the NW diameter (Dtop = 350 nm, Dbot = 700 nm) and center-to-center distance (Ptop = 500 nm, Pbot = 1000 nm), as well as making use of the waveguide properties of NWs and back surface reflectors.

Area 7: Christophe Allaud, Airbus OneWeb Satellites

Low Cost Applied to Large Space Constellations

Christophe Allaud is currently a manager for Airbus OneWeb Satellites Electronics Design to Cost & Technology. He is responsible of all One Web satellite electronics development (platform & payload units) with the aim to reduce the cost. He is also responsible for new technologies development and assessment of non-space technologies with regards to the Oneweb mission specifications. Prior to joining Airbus, he was a consultant for both Matra Marconi Space and Alcatel Space Industries. His background and expertise span power electronics, array & battery design, RF devices and payload management.

Area 8: Christophe Ballif, EPFL and CSEM, Switzerland

Novel designs and materials for durable PV modules: applications on the ground, in cities and in the air

Christophe Ballif received his Ph.D. degree in physics in 1998 in Lausanne, Switzerland. After Stays at NREL, Fraunhofer ISE and EMPA, he became in 2004 Full Professor with the Institute of microengineering, University of Neuchâtel, Switzerland, directing the Photovoltaics and Thin-Film Electronics Laboratory. In 2009, the Institute became part of EPFL. Since 2013, he has also been the Director of the PV-Center within CSEM, Neuchâtel, an RTO specialized in industrial research and technology transfer. His research interests include materials for PV, high-efficiency c-Si solar cells and silicon heterojunction cells, multi-junction solar cells, module technology, BIPV, and Energy systems. Christophe Ballif is the laureate of the 2016 Becquerel Prize.

The purpose of this study is to investigate the role of SiNx in PID for p-type crystalline Si cells. PID tests for the modules using the cells with different thicknesses of SiNx, including the cell without SiNx, were carried out. Comparing the modules with 70 nm thick SiNx and 140 nm thick SiNx, the degradation of the module with 140 nm thick SiNx is more slowly down than the module with 70 nm thick SiNx. Also, PID did not occur with the module using the cell without SiNx even if the voltage of -2000 V was applied for 1 week. From the simulation results of electric field distribution under applied voltage for the modules using the cells with and without SiNx, electric field is not applied to the cell surface in the case of the module using cell without SiNx. It has been reported yet that the composition of SiNx affects PID. However, in this study, it was found that PID progress is different even if the composition of SiNx is the same but only the thickness is changed. In addition, PID does not occur in the case of the modules using the cell without SiNx. From these results, it is shown that the behavior of PID strongly depends on the characteristics of anti-reflection coating. Therefore, it is concluded that no electric field applied to SiNx is the most important to prevent PID.

Area 9: T. John Trout, DuPont Photovoltaic Solutions

John is the R&D Manager for PV Reliability for DuPont Photovoltaic Solutions, leading the global program in PV Reliability that includes module and material accelerated testing, evaluation of modules from fields around the world, and the development of codes and standards. DuPont’s Photovoltaic Solutions team spans the globe with laboratories in the US, China, and Japan and with additional personnel in Europe and India. They have been leading an effort to understand field degradation mechanisms, share this information through publications and presentation and drive sensible standards through participation with IEC TC82 WG2, UL, ANSI, and PVQAT. John has worked in Photovoltaics for 8 years and has worked for DuPont for 31 years. Prior to PV, John worked in a number of new business ventures and helped start and launch two new businesses for DuPont. His background includes R&D, and Sales and Marketing. John holds a Ph.D. in Physical Chemistry from the University of Pennsylvania and BS in Chemistry from Davidson College.

We report on the fabrication and electronic and device properties of inorganic cesium-lead mixed halide perovskite solar cell. The p-i-n devices were deposited using a layer-by-layer technique, where alternate layers of cesium bromide and lead iodide were deposited using vacuum deposition. The p heterojunction layer was PTAA and the n heterojunction layer was PCBM. It was discovered that in order to get the best devices, the individual thicknesses of each of the layers had to be small (4 nm and 5 nm respectively). Multiple stacks of alternating layers made up the device, with the total thickness of the perovskite varying between 400 and 800nm. After deposition, the films were annealed at different temperatures to allow for diffusion and formation of the stoichiometric perovskite layer. It was found that when the individual layers were thin, one could obtain the stoichiometric perovksite by annealing at 250 C for 3 minutes, whereas thicker layers (eg 20 nm CsBr2 and 25 nm PbI2) needed annealing at higher temperatures (~350 C). The ebst devices were obtained by using thin alternating layers. The devices showed a voltage of 1.2 V, a current density of 12 mA/cm2 and a fill factor of 70% for a device efficiency of ~10%. Quantum efficiency spectroscopy showed a bandgap of 1.9 eV and subgap quantum efficiency revealed an Urbach energy of valence band tails to be ~20 meV.

Area 10: Tom Bialek, San Diego Gas & Electric Co.

The Role of Power Electronics in Mitigating Intermittent Renewables

Tom received a Bachelor and Master of Science Degree in Electrical Engineering from the University of Manitoba in 1982 and 1986 respectively. He also obtained a Doctor of Philosophy in Electrical Engineering from Mississippi State University in 2005. He is currently employed by San Diego Gas & Electric Company ("SDG&E") as a Chief Engineer. His present responsibilities involve technology strategy and policy for transmission and distribution issues including equipment, operations, planning, distributed generation and development of new technologies. He was also the Principal Investigator on DOE and CEC funded Micro Grid projects. He is a frequently requested external speaker and DOE R&D peer reviewer. Tom was also recognized by Greentech Media in its inaugural 100 Top Movers and Shakers in Smart Grid. In 2009 Tom was recognized with SDG&E’s Cornerstone award and in 2010 received the Outstanding Engineer award from the San Diego County Engineering Council.

Contact passivation in silicon solar cells is currently a very popular topic in the PV community. One method is via the deposition of thin tunneling layer alongside highly doped polysilicon. However, contacts which are based on thin p+ polysilicon layers have been facing compatibility issues with the standard screen-printing & firing process, as conventional metal pastes would penetrate through the polysilicon layer and thus reach the bulk material. In this work we demonstrate that a solar cell with p+ polysilicon layer can be properly metalized by industrial screen printing & firing process by forming the polysilicon tunnel junction. Characterization of tunnel junctions with and without interfacial SiOx layer shows rear J0 values of ~82 fA/cm2 and ~101 fA/cm2, respectively. This indicates that the formation of tunnel junctions did not adversely affect the passivation quality of the solar cell. Furthermore, it was found that additional interfacial SiOx between the polysilicon layers further improves the passivation quality but increases the tunneling resistance. Several improvements have been suggested for further improvement of tunneling resistance as well as solar cell performance. The tunnel junctions developed in this work were fabricated using industrial tools and can also be directly applied for two-terminal tandem integration applications.

Area 11 Stephen Steffel, Pepco Holdings, Inc.

Distribution Grid Innovation being Driven by PV Solar Integration

Stephen Steffel is the Manager of Distributed Energy Resources Planning and Analytics at Pepco Holdings, Inc. Pepco Holdings (PHI), a subsidiary of Exelon Corporation, is one of the largest energy delivery companies in the Mid-Atlantic region, serving more than 2 million customers in Delaware, the District of Columbia, Maryland and New Jersey. He received his MBA from the University of Baltimore and BS in Mechanical Engineering from Drexel University.

Solar cell performances at low light intensities are practically more important for power generation capacity in the entire life. Previous studies have revealed that efficiency and maximum power of solar cells with low shunt resistance become lower at the low light intensities. In contrast, our previous studies have clarified each specific effect of constituents in conductive paste on the shunt resistance, recombination, and open-circuit voltage (Voc) of solar cells with “floating contact method”. However, effects of the paste constituents on the low light performances have not been actually clear yet. For this reason, in this study, effects of glass frit itself, which is an indispensable paste constituent, on the low light performances of the cells are investigated. The glass frit itself makes solar cell efficiency much lower at lower light intensities, which comes from its effects on Voc and fill factor (FF) of the cells; specifically, the frit makes not only the Voc, but also the FF lower at the lower intensities. Our previous study showed that the glass frit itself causes drastic shunts and recombination in the solar cells; therefore, its effects on the Voc at the lower intensities are reasonable, but the frit decreases also the FF. Glass frit, however, is an indispensable constituents for silver paste to reduce the solar cell production cost, because the frit enables the paste to make conductive passes between the paste metallization and emitter by firing-only. Hence, advancing glass frit is a key to satisfy both of cost reduction and high efficiency, as well as power generation capacity in the entire life.

Area 12 Becca Jones-Albertus, US Department of Energy

Scaling Up Solar Deployment

Dr. Becca Jones-Albertus is the Acting Deputy Director for the U.S. Department of Energy’s Solar Energy Technologies Office and SunShot Initiative, which are working to accelerate the market competitiveness of solar energy by targeting LCOE reductions and increased solar deployment. Dr. Jones-Albertus has spent her career advancing photovoltaic materials and devices, from fundamental research and development to technology transfer into manufacturing. Prior to joining the Department of Energy, Dr. Jones-Albertus was the Characterization and Design Manager at Solar Junction, where she led efforts developing the company’s two-time world record solar cells and then transferring that technology to a high volume manufacturing toolset. She has eight patents and more than 30 technical publications. Dr. Jones-Albertus graduated magna cum laude from Princeton University with a B.S. in electrical engineering, and also holds a M.S. and Ph.D. in materials science and engineering from the University of California, Berkeley.

Arcing in photovoltaic (PV) power systems is a significant concern due to the potential for property damage from a PV system fire and personal safety from electrical shock hazard or electrocution if an arc is undetected and left unmitigated. Arc fault detectors are now required by the new National Electric Code and Underwriters Laboratories (UL) standard 1699B which was developed to address testing and listing requirements for these devices. One significant challenge that arose in developing the UL1699B standard was the way in which an arc was created to test the arc fault detector. The test needed to faithfully replicate a real-world arcs yet also be scientifically repeatable in the laboratory. While UL standards, test protocols, and test beds exist for AC-system arc fault detectors, arcs in DC systems, particularly PV, are different. This paper reports on the results of a project to develop a DC arc generator (AG) suitable for use in the development and testing of DC arc fault detectors.